1. Field of the Invention
The present application relates to a substrate for an ink jet recording head adapted to record information by ejecting an ink onto an ink jet recording medium, and a method for manufacturing the same. This substrate is hereinafter referred to as the ink jet recording head substrate. The present application also relates to an ink jet recording head including the ink jet recording head substrate.
2. Description of the Related Art
A thermal ink jet recording head has recently been desired which can operate at low power with reliability. A thermal ink jet recording head (hereinafter simply referred to as the ink jet recording head) includes an element substrate for the ink jet recording head, and a liquid flow channel member having an ink chamber and ink ejection openings communicating with the ink chamber. The element substrate is provided with a heating resistor that applies heat for generating bubbles in an ink that are the energy for ejecting the ink. The heating resistor is provided with a protective layer thereon for preventing the heating resistor from coming into contact with the ink. In addition, an insulating layer is disposed between the base member, such as a silicon substrate, of the element substrate and the heating resistor. It is effective in operating the ink jet recording head at low power to reduce the thermal conductivity of the insulating layer disposed between the heating resistor and the semiconductor substrate, or base member. The insulating layer on the semiconductor substrate is generally made of silicon oxide having a thermal conductivity of 1.3 W·m−1·K−1. An insulating layer having a lower thermal conductivity than silicon oxide, that is, a heat accumulation layer is desired.
In the case of using a heat accumulation layer having a low thermal conductivity, heat generated from the heating resistor does not easily dissipate in the direction of the semiconductor substrate through the heat accumulation layer. This is efficient in increasing the temperature of the thermal operation portion, which will come into contact with the ink, on the heating resistor, accordingly reducing the energy applied for bubbling the ink. Consequently, the resulting recording head can operate at low power.
The ink jet recording head disclosed in U.S. Pat. No. 7,390,078 includes an insulating layer 28, a heat accumulation layer (low thermal diffusivity film) 32, a heating resistor layer 26, a covering layer (electroconductive metal layer) 60 and a protective layer 30 on a substrate 22, as shown in FIG. 5. In this head, the plane between the protective layer 60 and the heating resistor layer 26 acts as a fluid ejector actuator 17. The insulating layer 28 is made of, for example, silicon oxide or silicon nitride, and the heat accumulation layer 32 is made of an aerogel of a ceramic oxide, such as silica, titania, or alumina. The heat accumulation layer 32 has very small pores of less than 100 nm in pore size, and a low thermal conductivity of about 0.3 to 1 W·m−1·K−1. Thus, the ink jet recording head can operate at low power. For the other reference numerals in FIG. 5, see the above-cited U.S. Pat. No. 7,390,078.